Recently in audio field, a digital audio tape recorder (DAT) has appeared on the market, and in VTR field, an 8 mm width tape that is narrower than a conventional half-inch width tape has appeared and is getting popular now. Under the above-mentioned circumstances, the magnetic recording media capable of higher density recording are required increasingly. There is growing a demand for a magnetic recording medium having high efficiency, namely, excellent electromagnetic conversion characteristics and running durability.
In order to meet the foregoing requirement to improve the electromagnetic conversion characteristics of magnetic recording media, a fine ferromagnetic powder has come to be used, however, it still has a poor dispersibility problem when used in magnetic layers.
To be more concrete, the magnetic recording media containing fine ferromagnetic powder have the following problems; (1) electromagnetic conversion characteristics are not necessarily satisfactory; (2) a part of ferromagnetic powder particles of poor dispersion is liable to drop out during a running operation; (3) a part of particles dropped out in travelling is liable to adhere momentarily to a magnetic head and cause the so-called `instant head clog`, which is then liable to reduce a reproducing output; and so forth.
To solve the above-mentioned problems, there have been proposed the magnetic recording media, for example, comprising ferromagnetic metal powder having an adsorbed moisture of not more than 1.2 wt %, which is disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 61-8726/1986.
However, the above-given particular magnetic recording medium still has a problem of an increased viscosity of a magnetic paint.
To be more concrete, an increase in a viscosity of a magnetic paint will cause the following disadvantages, for example, (1) a magnetic paint is difficult to transfer smoothly in a transferring line in manufacturing magnetic recording media, and partial clogging of the paint in the transferring line is liable to happen; (2) such unstable production sometimes results in bad product quality such as drop out of a magnetic layer, which results in deterioration of electromagnetic conversion characteristics; (3) after coating a magnetic paint on a non-magnetic support in a coating step, it is difficult to carry out smoothly a surface smoothing process, and a surface smoothness of a magnetic recording medium is liable to be damaged as so seriously to cause head clogging, edge-fold or the like troubles and to lower a running durability of a recording medium; and so forth.
Such a magnetic recording medium is expected to be commercialized as having excellent running durability and electromagnetic conversion characteristics attributable to good dispersibility of a ferromagnetic metal powder and stable manufacturing.
Based upon the above-mentioned circumstances, this invention has been made.
It is, therefore, an object of the invention to provide a magnetic recording medium which can be manufactured stably because of good dispersibility of a ferromagnetic metal powder and comprises high electromagnetic conversion characteristics as well as an excellent durability.